The present application relates generally to combinations of compounds and methods for treating upper gastrointestinal tract disorders. More particularly, the present application relates to the use of at least one bile acid sequestrant for treating esophageal disorders.
The esophagus carries food, liquids, and saliva from the mouth to the stomach by coordinated contractions of its muscular lining. This process is automatic and people are usually not aware of it. Many people have felt their esophagus when they swallow something too large, try to eat too quickly, or drink very hot or very cold liquids. They then feel the movement of the food or drink down the esophagus into the stomach, which may be an uncomfortable sensation.
The muscular layers of the esophagus are normally pinched together at both the upper and lower ends by muscles called sphincters. When a person swallows, the sphincters relax automatically to allow food or drink to pass from the mouth into the stomach. The muscles then close rapidly to prevent the swallowed food or drink from leaking out of the stomach back into the esophagus or into the mouth. These sphincters make it possible to swallow while lying down or even upside-down. When people belch to release swallowed air or gas from carbonated beverages, the sphincters relax and small amounts of food or drink may come back up briefly; this condition is called reflux. The esophagus quickly squeezes the material back into the stomach. This amount of reflux and the reaction to it by the esophagus are considered normal.
While most people are familiar with acid reflux—the backflow of caustic stomach acids into the esophagus—bile reflux, which occurs when bile—a digestive fluid produced in the liver—flows upward (refluxes) from the small intestine into the stomach and esophagus, is less well known. Bile reflux often accompanies acid reflux, and together may lead to inflammation of the esophageal lining and potentially increased risk of esophageal cancer. See MG (1999) 94(12):3649-3650. Bile reflux also affects the stomach, where it causes further inflammation.
Unlike acid reflux, bile reflux usually can't be controlled by changes in diet or lifestyle. Instead, bile reflux is most often managed with certain medications or, in severe cases, with surgery. Neither solution is uniformly effective, however, and some people continue to experience bile reflux even after treatment.
Bile reflux can be difficult to distinguish from acid reflux—the signs and symptoms are similar, and the two conditions frequently occur at the same time. Unlike acid reflux, bile reflux inflames the stomach, often causing a gnawing or burning pain in the upper abdomen. Other signs and symptoms may include: frequent heartburn, i.e., a burning sensation in the chest that sometimes spreads to the throat along with a sour taste in the mouth; nausea; vomiting bile; a cough; or hoarseness.
Bile and stomach acid reflux into the esophagus when the lower esophageal sphincter (LES), malfunctions. The LES separates the esophagus and stomach. Normally, it opens only to allow food to pass into the stomach and then closes tightly. But if the valve relaxes abnormally or weakens, stomach acid and bile can wash back into the esophagus, causing heartburn and ongoing inflammation that may lead to serious complications.
A sticky mucous coating protects the stomach from the corrosive effects of stomach acid, but the esophagus lacks this protection, which is why bile reflux and acid reflux can seriously damage esophageal tissue. And although bile reflux can injure the esophagus on its own—even when the pH of the reflux is neutral or alkaline—the combination of bile and acid reflux seems to be particularly harmful, increasing the risk of complications, such as: Gastroesophageal reflux disease, or GERD; Barrett's esophagus; esophageal cancer, and gastritis.
GERD is a generic term encompassing diseases with various digestive symptoms such as pyrosis, acid regurgitation, obstructed admiration, aphagia, pectoralgia, permeating feeling and the like sensibility caused by reflux in the esophagus and stagnation of gastric contents, duodenal juice, pancreatic juice and the like. The term covers both of reflux esophagitis in which erosion and ulcers are endoscopically observed, and esophageal regurgitation-type non-ulcer dyspepsia (NUD) in which no abnormality is endoscopically observed. GERD occurs when the LES does not close properly and stomach contents leak back, or reflux, into the esophagus.
A hiatal hernia may contribute to causing GERD and can happen in people of any age. Other factors that may contribute to GERD include, but are not limited to, alcohol use, overweight, pregnancy, smoking, Zollinger-Ellison syndrome, hypercalcemia, and scleroderma. Also, certain foods can be associated with reflux events, including, citrus fruits, chocolate, drinks with caffeine, fatty and fried foods, garlic and onions, mint flavorings, spicy foods, and tomato-based foods, like spaghetti sauce, chili, and pizza.
The inner mucosa of the esophagus is lined with nonkeratinized stratified squamous epithelium arranged in longitudinal folds. Damage to the lining of the esophagus causes the normal squamous cells that line the esophagus to turn into a type of cell not usually found in humans, called specialized columnar cells. That conversion of cells in the esophagus by the acid reflux, is known as Barrett's Esophagus. Although people who do not have heartburn can have Barrett's esophagus, it is found about three to five times more often in people with this condition. Barrett's esophagus does not cause symptoms itself and is important only because it seems to precede the development of a particular kind of cancer—esophageal adenocarcinoma. The risk of developing adenocarcinoma is 30 to 125 times higher in people who have Barrett's esophagus than in people who do not. This type of cancer is increasing rapidly in white men. This increase may be related to the rise in obesity and GERD.
Barrett's esophagus has no cure, short of surgical removal of the esophagus, which is a serious operation. Surgery is recommended only for people who have a high risk of developing cancer or who already have it. Most physicians recommend treating GERD with acid-blocking drugs, since this is sometimes associated with improvement in the extent of the Barrett's tissue. However, this approach has not been proven to reduce the risk of cancer. Treating reflux with a surgical procedure for GERD also does not seem to cure Barrett's esophagus. Several different experimental approaches are under study. One attempts to see whether destroying the Barrett's tissue by heat or other means through an endoscope can eliminate the condition. This approach, however, has potential risks and unknown effectiveness.
Esophageal cancer can occur almost anywhere along the length of the esophagus, but it frequently starts in the glandular cells closest to the stomach (adenocarcinoma). Because esophageal cancer may not be diagnosed until it's quite advanced, the outlook for people with the disease is often poor. The risk of cancer of the esophagus is increased by long-term irritation of the esophagus, such as with smoking, heavy alcohol intake, and Barrett's esophagitis. Thus, there is a link between esophageal cancer and bile reflux and acid reflux. In animal models, bile reflux alone has been shown to cause cancer of the esophagus.
There are numerous medications available that can effectively treat heartburn and indigestion. Presently, the main therapies employed in the treatment of GERD and upper GI tract disorders include agents for reducing the stomach acidity, for example by using the histamine H2-receptor antagonists or proton pump inhibitors (PPIs). H2 blockers are drugs that inhibit the production of acid in the stomach. Exemplary histamine H2-receptor antagonists include, for example, cimetidine (as sold under the brand-name TAGAMET HB®), famotidine (as sold under the brand-name PEPCID AC®), nizatidine (as sold under the brand-name AXID AR®), and ranitidine (as sold under the brand-name ZANTAC 75®). Both types of medication are effective in treating heartburn and usually eliminate symptoms within a short period of time.
PPIs act by inhibiting the parietal cell H+/K+ ATPase proton pumps responsible for acid secretion from these cells. PPIs, such as omeprazole, and its pharmaceutically acceptable salts are disclosed, for example, in EP 05129, EP 124495 and U.S. Pat. No. 4,255,431.
Despite their well-documented efficacy, PPIs have notable limitations. These drugs exhibit substantial inter-patient variability in pharmacokinetics and may have significant interactions with other drugs. For example, patients who are non-responsive to treatment with PPI inhibitor alone may be non-responsive because even though the PPI is decreasing acid reflux from the stomach, bile acid from the duodenum is still present. Thus, an improvement of PPI-mediated activity is a well-recognized challenge in gastroenterology and there is a need in the art to address and overcome upper GI tract disorders that are non-responsive to treatment by administration of PPIs alone.
Accordingly, the development of an effective treatment for pathologies in which inhibition of one or both of gastric acid secretion and bile acid secretion is required would be useful.